Trading kidneys, repugnant markets and stable marriages win the Nobel Prize in Economics

Roth and Shapley charted a course for economists to go beyond simply arguing for markets in everything.

The 2012 Nobel Prize in Economics - technically the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, but nobody cares - has been awarded to two American Economists, Alvin Roth and Lloyd Shapley "for the theory of stable allocations and the practice of market design". The Nobel Committee explains what that means:

This year's Prize concerns a central economic problem: how to match different agents as well as possible. For example, students have to be matched with schools, and donors of human organs with patients in need of a transplant. How can such matching be accomplished as efficiently as possible? What methods are beneficial to what groups? The prize rewards two scholars who have answered these questions on a journey from abstract theory on stable allocations to practical design of market institutions.

Lloyd Shapley used so-called cooperative game theory to study and compare different matching methods. A key issue is to ensure that a matching is stable in the sense that two agents cannot be found who would prefer each other over their current counterparts. Shapley and his colleagues derived specific methods – in particular, the so-called Gale-Shapley algorithm – that always ensure a stable matching. These methods also limit agents' motives for manipulating the matching process. Shapley was able to show how the specific design of a method may systematically benefit one or the other side of the market.

Alvin Roth recognized that Shapley's theoretical results could clarify the functioning of important markets in practice. In a series of empirical studies, Roth and his colleagues demonstrated that stability is the key to understanding the success of particular market institutions. Roth was later able to substantiate this conclusion in systematic laboratory experiments. He also helped redesign existing institutions for matching new doctors with hospitals, students with schools, and organ donors with patients. These reforms are all based on the Gale-Shapley algorithm, along with modifications that take into account specific circumstances and ethical restrictions, such as the preclusion of side payments.

Even though these two researchers worked independently of one another, the combination of Shapley's basic theory and Roth's empirical investigations, experiments and practical design has generated a flourishing field of research and improved the performance of many markets. This year's prize is awarded for an outstanding example of economic engineering.

The committee have yet again reaffirmed the old adage that the most important thing to do when trying for a nobel prize is to live long enough that your achievements are recognised. The Gale-Shapley algorithm, for instance, was devised in 1962, when Lloyd Shapley was 34. It concerns a maths problem known as the stable marriage problem: if you have an even number of men and women, can you always come up with a set of marriages where there are no two people of opposite sex who would both rather have each other than their current partners? (1960s maths problems: usually heteronormative.) If you can, then the marriage is "stable".

The Gale-Shapley algorithm is a way of always ensuring stable matches; and much of Shapley's work covers the same areas, straddling the boundaries between economics, mathematics, and computer science.

Roth is the younger of the two winners, and works in a far more empirical sphere. As the committee points out, although the two men never actually collaberated, Roth took Shapley's theoretical work and applied it to actually existing markets. For instance, Roth used the Gale-Shapley agorithm to ease the kidney shortage in the US. David Wessel explains (£):

As of noon yesterday, 58,470 people in the U.S. were waiting for a kidney transplant. Most won't get one this year. There aren't enough donated kidneys to go around. Surgeons transplanted just 15,129 kidneys last year. Now a band of transplant surgeons and economists are trying to fix that by creating a moneyless market for exchanging kidneys. Most transplanted kidneys come from a person who has died, a supply that grows slowly because of ignorance about the need for donations or grieving relatives' reluctance. But a kidney taken from a live donor works better, and almost everyone has a spare. As techniques improve for removing healthy kidneys and for suppressing the body's tendency to reject a transplant, doctors increasingly turn to kidneys from living donors, usually relatives. Last year, 43% of kidneys transplanted in the U.S. came from living donors, up from 28% a decade ago. But a biological barrier often blocks a transplant from a relative. In about a third of all would-be pairs, blood types are incompatible. In others, the sick person has antibodies that can initiate a rejection of the donated organ. It's heartbreaking "to have the treasure of the live donor and then have that not go forward because of a biological obstacle," says Massachusetts General Hospital transplant surgeon Francis DelMonico.

Occasionally, transplant centers spot a way out: One New England father with blood type A couldn't donate a kidney to his daughter with blood type B. So he gave a kidney to a teenager with blood type A, and the teenager's sister gave a kidney for the man's daughter. New England's transplant centers have done six such exchanges. Baltimore's Johns Hopkins University has done seven.

The crucial thing about Roth's work, from an economic point of view, is that it involves finding stable allocations using market-like situations without involving money. The kidney swaps in the New England situation are market-like, trading kidneys for kidneys in a way that makes all parties better-off, but they don't actually require kidneys to be bought and sold.

We can see the importance of this by looking at another paper of Roth's, not cited by the committee, on repugnance in markets (pdf). Roth demonstrates that some markets are limited because the very existance of a market in some goods is considered repugnant. He argues, for instance, that the trade in horse meat being banned in California is not done through fears that eating horse meat is unsafe; nor is it done for animal welfare reasons, since it is still legal to farm and kill horses. But banned it is, and Roth argues that the natural response of economists to situations of this type - to argue for freer markets - is wrong, since it ignores the very strong feelings involved in the situation. Instead:

Being aware of the sources of repugnance can only help make such discussions more productive, not least because it can help separate the issues that are fundamentally empirical—like the degree of crowding out of altruistic donations that might result from different incentive schemes compared to how much new supply might be produced—from areas of disagreement that are not primarily empirical.

Hopefully his new Nobel Prize should give that argument greater weight in the years ahead.

A patient receives a kidney in Johns Hopkins university in Baltimore. Photograph: Getty Images

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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Commons Confidential: Fearing the Wigan warrior

An electoral clash, select committee elections as speed dating, and Ed Miliband’s political convalescence.

Members of Labour’s disconsolate majority, sitting in tight knots in the tearoom as the MP with the best maths skills calculates who will survive and who will die, based on the latest bad poll, observe that Jeremy Corbyn has never been so loyal to the party leadership. The past 13 months, one told me, have been the Islington rebel’s longest spell without voting against Labour. The MP was contradicted by a colleague who argued that, in voting against Trident renewal, Corbyn had defied party policy. There is Labour chatter that an early general election would be a mercy killing if it put the party out of its misery and removed Corbyn next year. In 2020, it is judged, defeat will be inevitable.

The next London mayoral contest is scheduled for the same date as a 2020 election: 7 May. Sadiq Khan’s people whisper that when they mentioned the clash to ministers, they were assured it won’t happen. They are uncertain whether this indicates that the mayoral contest will be moved, or that there will be an early general election. Intriguing.

An unguarded retort from the peer Jim O’Neill seems to confirm that a dispute over the so-called Northern Powerhouse triggered his walkout from the Treasury last month. O’Neill, a fanboy of George Osborne and a former Goldman Sachs chief economist, gave no reason when he quit Theresa May’s government and resigned the Tory whip in the Lords. He joined the dots publicly when the Resolution Foundation’s director, Torsten Bell, queried the northern project. “Are you related to the PM?” shot back the Mancunian O’Neill. It’s the way he tells ’em.

Talk has quietened in Westminster Labour ranks of a formal challenge to Corbyn since this year’s attempt backfired, but the Tories fear Lisa Nandy, should the leader fall under a solar-powered ecotruck selling recycled organic knitwear.

The Wigan warrior is enjoying favourable reviews for her forensic examination of the troubled inquiry into historic child sex abuse. After Nandy put May on the spot, the Tory three-piece suit Alec Shelbrooke was overheard muttering: “I hope she never runs for leader.” Anna Soubry and Nicky Morgan, the Thelma and Louise of Tory opposition to Mayhem, were observed nodding in agreement.

Select committee elections are like speed dating. “Who are you?” inquired Labour’s Kevan Jones (Granite Central)of a stranger seeking his vote. She explained that she was Victoria Borwick, the Tory MP for Kensington, but that didn’t help. “This is the first time you’ve spoken to me,” Jones continued, “so the answer’s no.” The aloof Borwick lost, by the way.

Ed Miliband is joining Labour’s relaunched Tribune Group of MPs to continue his political convalescence. Next stop: the shadow cabinet?

Kevin Maguire is Associate Editor (Politics) on the Daily Mirror and author of our Commons Confidential column on the high politics and low life in Westminster. An award-winning journalist, he is in frequent demand on television and radio and co-authored a book on great parliamentary scandals. He was formerly Chief Reporter on the Guardian and Labour Correspondent on the Daily Telegraph.

This article first appeared in the 27 October 2016 issue of the New Statesman, American Rage